Stormwater pipes are generally found to be in significantly worse condition than sewer pipes when it comes to rehabilitation. However, little funding has been put towards these assets in the past, with more focus placed on sewers which can have a much higher environmental impact. But stormwater pipes play a significant role in property damage by causing ground subsidence, structural cracks in properties, and localised flooding. The problems are generally exacerbated by the fact that stormwater pipes are mostly shallow and in close proximity to above ground structures.

In 2011, it has been pleasing to see more funds going into the repair of these important and badly deteriorated assets in Sydney. However, the most critical works have been found in the oldest areas of Sydney, including the CBD, Darlinghurst, Petersham, Redfern, Waterloo, Annandale, Leichhardt and Moore Park. Therefore, careful planning and appropriate mitigation measures have to be put in place to minimise disturbance to commercial businesses and residential properties.

Here the company profiles a number of interesting recently completed projects.

NSW Parliament House and Royal Botanic Gardens

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The upstream maintenance hole (MH) of a 450 mm pipe was located directly behind Parliament House, near a couple of other critical stakeholders including the State Library and Sydney Hospital. The downstream MH was found in the Royal Botanic Gardens (RBG), where many Sydney-siders enjoy a stroll, jog, or picnic on a beautiful Sydney day.

Communication with RBG and Parliament House was crucial as the parking bays on Hospital Road had to be reserved, and noise impact minimised.

Initial CCTV footage revealed a large break with root intrusion behind Parliament House, as well as an even larger break with only steel reinforcement remaining. Insituform’s crews spent a day carrying out robotic works on the pipe, as well as very careful cleaning in preparation for lining. The pipe was then lined in a single day using Insituform’s renowned air inverted/steam cured CIPP system, resulting in a tight-fitting, joint-less, corrosion-resistant structural liner.

Bourke Street, Darlinghurst

This 300 mm pipe was located in the heart of Darlinghurst, near Taylor Square, and traffic control was crucial to gaining access to the MHs on Bourke Street. Insituform ensured all stakeholders were notified, including local pubs, terrace houses, a school, and even the District Court on Oxford Street.

Initial CCTV footage revealed the pipe had bends, large displacements requiring robotic grinding, as well as large pieces of concrete and debris sitting in the invert. After robotic preparation and cleaning works, Insituform was again able to install one of its CIPP liners using air inversion/steam curing in a single day shift, reducing the original pipe diameter by only 5 per cent, while actually increasing flow capacity due to the improved hydraulics through the smooth joint-less liner. More importantly, the liner was installed through the bends without the need to civil works.

Petersham Park

This 200 m long section of 600 mm pipe ran under historic Petersham Park, the same oval where Don Bradman made his first class debut and century in the same match.

Initial CCTV footage revealed a multitude of problems including severe structural deterioration and pipe breaks. To make the situation worse, the pipe had large amounts of hard cementitious grout throughout the invert, as well as three unexpected buried chambers that needed to be exposed prior to lining.

Insituform worked closely with Marrickville Council to put a plan in place to minimise the impact of works, as the oval is used by the community for sporting events and training. Insituform successfully completed the chamber raising works, and robotic removal of grout from the pipe in preparation for lining.

The lining was again completed using Insituform’s CIPP liners by air inversion/steam curing. Despite the number of chambers and MHs involved, the 200 m was completed in just two installations over two day shifts, with minimal disruption to the park and the community.

CIPP success

Thanks to the invention of Insituform’s CIPP technology 40 years ago by company founder Eric Woods, the days of digging and replacing pipes are long gone. Even severely deteriorated stormwater pipes can be cost-effectively salvaged and renewed by CIPP lining.

These Sydney projects demonstrate that CIPP lining is an affordable, reliable, and non-disruptive solution for sewer or stormwater pipe renewal. Repairs are completed quickly which results in less impact to the local environment and community.